He slammed SAP's Oracle-killer database HANA on a conference call with analysts like this:

"SAP does not use HANA in the cloud very much. I know that because they keep paying us. They paid us again, this quarter, for Oracle for Concur, Oracle for Ariba, Oracle for SuccessFactors," he said, naming three cloud companies that SAP acquired over the past few years to jump start its cloud business.

"If they're using HANA for anything, I don't know about it," Ellison chuckled.

Ariba, SuccessFactors, and Concur obviously built some of their systems on the Oracle database before they were acquired by its biggest rival, SAP.

Like other Oracle customers, SAP must have found that it isn't easy to rip and replace a database, even though it must be excruciating to write checks to Oracle.

One of Oracle's CEOs, Safra Catz, explained why Oracle doesn't have that problem. Oracle makes all the hardware and software it needs to build its own cloud. This means that Oracle's cloud can be run more profitably than competitors, she said.

As the two companies became more competitive, and the two men had a falling out, Salesforce was rumored to be trying to move to an open source database known as Postgres. That would have been a bad precedent for Oracle, showing other cloud companies how they could migrate off Oracle, too.